The invention relates to the method, architecture and interfaces that allow synchronous transfer mode (STM) traffic to be efficiently transported via an asynchronous transfer mode (ATM) network.
In telecommunications systems, the protocol utilized for offering a wide range of high-bandwidth services, e.g., multimedia services, may be based on Asynchronous Transfer Mode (ATM) protocols. These protocols define a particular data structure called a xe2x80x9ccellxe2x80x9d, which is a data packet of a fixed size (e.g., 53 octets, each comprising eight bits).
Typically, ATM standards are based on signaling schemes designed to accommodate multimedia applications. The recent research into advance ATM network architectures has been conducted as illustrated by U.S. Pat. No. 5,588,475, U.S. Pat. No. 5,483,527, and U.S. patent application No., entitled An ATM Network Arranged to Interface with STM In-Band Signaling, filed on Dec. 21, 1994, to Doshi et al., and assigned case number 10-2-5-2-2-2-2. Conventional approaches include the use of statistical multiplexing including voice compression in an ATM environment. However, these approaches may require the introduction of Variable Bit Rate (VAR.) capabilities, including sophisticated signaling mechanisms and a different ATM adaptation layer, AAL-2. None of the conventional approaches provide for ATM call set-up using standard signaling systems, traffic management between a terminal adapter and an ATM switch, or variable background noise.
The invention includes various architectures, structures, and methods for addressing the above mentioned problems. In accordance with aspects of the invention, fax, voice and data calls may be efficiently processed by an Asynchronous Transfer Mode (ATM) switch by re-using a conventional Synchronous Transfer Mode (STM) network signaling system. A standard ATM AAL-1 adaption layer may be utilized to accomplish voice compression. STM-to-ATM call translation may be accomplished by a mapping that is determined based on a Virtual Path/Virtual Circuit occupancy status to take full advantage of available bandwidth by eliminating marked cells.
Our research disclosed in this application has advanced the state of the art by specifying the specific architectures which enable STM to ATM interfaces and which allow a Constant Bit Rate (CBR) call in an ATM domain using existing (i.e., STM in-band or out-of-band) signaling mechanisms to forward a call to its destination. Architectures in accordance with the present invention facilitate the use of ATM technology to carry traditional voice, fax and voice-band data traffic and demonstrate that the evolution to broadband signaling is not necessary in the initial period of STM-to-ATM transition.
Our proposals define network architecture and ATM capabilities required to transport voice efficiently in the ATM domain. It exploits STM network signaling and modifies standard ATM adaptation layer AAL-1 to achieve voice compression. Specifically, to eliminate silence, we augment the cell-building process with appropriate cell marking. In the case of congestion, marked cells that do not contain voice signals are discarded by either the Terminal Adapter or the ATM switch.
We also describe specific rules for STM-to-ATM call routing translation. This mapping may be determined at each instance based on the Virtual Path/Virtual Circuit (VP/VC) occupancy status to take full advantage of the potentially available bandwidth (no marked cells). We also define a method for obtaining and monitoring VP/VC/buffer occupancy data that allows the ATM switch to control bandwidth usage and prevent performance degradation associated with cell loss (a third key idea).
Our proposal results in bandwidth (transport) and switch termination savings and could be applicable in a variety of wide area or local area network settings and in the PABX to ATM environment.